1. Technical Field
The present disclosure relates to the verification of a device using a plurality of power sources having different voltage levels and, more particularly, to a method of verifying operational characteristics of a device depending on supply or block of a plurality of power sources at a register transfer level (RTL) and a method of modeling the power off effect at the RTL.
2. Discussion of Related Art
In apparatuses that are powered by built-in batteries, the power consumption should be minimized to effectively use the limited battery power over a period of time. Many apparatuses can be switched to a standby state when not in use. The amount of time that an apparatus is in a standby state can be longer than the time the apparatus is active. Only minimal power is consumed during standby mode, and the remaining power supply is blocked, so that the power consumed by the moving apparatus can be minimized. Instead of the voltage levels of power supplied to a plurality of devices comprising a mobile apparatus being identical with each other, different amounts of power can be supplied to devices capable of operating at low operating voltages and devices capable of operating only at high operating voltages, and the power consumption can be reduced.
The power supplied when a mobile apparatus operates normally and when the mobile apparatus is in a standby state can be distinguished from the power supplied when the mobile apparatus operates normally but may not be supplied when the mobile apparatus is in a standby state.
The input and output states of the devices not supplied with power in a standby state may affect a normal operation to which the standby state is later switched. To consume a minimal amount of power, mobile apparatuses should be designed in consideration of not only a distinction between various types of power and but also the case where power is supplied, the case where power is blocked, and the case where power is re-supplied after being blocked.
A Hardware Description Language (HDL) is a language used to describe the functions of a digital system for documentation, simulation or logic synthesis. In general, HDL languages can be used to design a digital system at behavior level, register transfer level (RTL), and at gate level. The behavior level describes a system by the functional characteristics of a device. A gate level model describes the function, timing, and structure of a component in terms of the structural interconnection of Boolean logic blocks. An RTL model is a model describing a system in terms of registers, combinational circuitry, low-level buses, and control circuits. Designs using the RTL specify the characteristics of a circuit by operations and the transfer of data between registers.
In a typical digital design process, verifying the logical correctness of a digital design and debugging the design are steps of the design process. For example, in the design of a digital system, operations of a device when the power sources are all supplied and when one or more of the power sources are not supplied can be verified through five steps as follows. First, a device model is defined at the register transfer level (RTL). Second, the operational characteristics of the device model are verified using a logic simulation program. Third, the device model confirmed through the verification is input to a logic synthesizer to produce a gate-level model of the device. Fourth, the operational characteristics of the gate-level model are verified using a logic simulation program. Fifth, the operational characteristics of the device model when the power sources are applied to the RTL device model and when the supply of the power sources are blocked are verified using a logic simulation program, which exercises the device model to detect logical errors in the digital design.
FIG. 1 illustrates a conventional verification environment for verifying a device model described at the RTL (hereinafter, referred to as “RTL device model 110”) using a logic simulation program. Referring to FIG. 1, the verification environment includes the RTL device model 110, a model 120 for producing an input signal of the RTL device model 110, and a model 130 for verifying an output signal of the RTL device model 110.
The RTL device model 110 is a model which describes, at the register transfer level, a device which performs a predetermined function. The model 120 produces a test pattern for testing the RTL device model 110. The model 130 produces an ideal response pattern, which is the desired output of the RTL device model 110, in response to the test pattern. The response pattern is compared with an actual output pattern that is output by the RTL device model 110. Thus, the response pattern is used in verifying the validity of the RTL device model 110.
A long period of time is required to produce a gate-level model of the device using a logic synthesizer. A long time is also required to verify the operation of the gate-level model using the logic simulation program. In particular, in step five of verifying the logical correctness of the digital design, it takes a long time to verify operations of the gate-level model of the device upon supply and non-supply of various types of power.
If it is determined in the fifth step, that a problem is generated when the device model is not supplied with power, the first step may be resumed, and the design period may be increased.